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This paper presents the development and optimization of a cost-effective paper electrochemical sensor for the detection of TNT using Fe 3 O 4 –Au core-shell nanoparticles modified with cysteamine (Fe 3 O 4 @Au/CA). The sensor was constructed by modifying a graphite paste with the aforementioned nanoparticles, which facilitated the formation of a Meisenheimer complex between cysteamine and TNT as an electron donor and an electron acceptor, respectively. The central composite design was employed to optimize four key parameters pH, modifier percentage, contact time, and buffer type to enhance the performance of the sensor. The detection limit was found to be 0.5 nM of TNT, while the linear range of the electrode response spanned from 0.002 μM to 10 μM. The simplicity and low cost of the sensor make it highly attractive for practical applications, particularly in scenarios where rapid and on-site TNT detection is required. [Display omitted] • Fabrication of a paper-based TNT sensor based on the Meisenheimer complexation. • Synergistic effect of Fe 3 O 4 @Au NPs improves the sensor's electrochemical properties. • The RSM-CCD optimization approach was used for the statistical optimization. • The detection limit of the sensor was 0.5 nM in the linear range of 0.002–10 μM. • The developed sensor can detect TNT in aqueous and soil samples, without extraction. [ABSTRACT FROM AUTHOR]

The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical polymerization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recognition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection. [ABSTRACT FROM AUTHOR]

Label-free electrochemical sensors have gained popularity as point-of-care devices because they do not require complicated labeling procedures. However, they have difficulties detecting multiple analytes simultaneously. In this study, we developed a novel label-free electrochemical immunosensor on an origami paper–based analytical device (oPAD) for the simultaneous detection of quinolone antibiotics, in which norfloxacin (Nor) and enrofloxacin (Enr) were used as a model. The oPAD was designed with two antibody zones, each zone contains different antibodies. The oPAD has two thionine- and ferrocenecarboxylic acid-coated reagent zones, as redox species, which will generate the response current signals for the detection of quinolone antibiotics. The simultaneous current responses of thionine and ferrocenecarboxylic acid decreased proportionately when exposed to Nor and Enr concentrations, respectively. Under optimal conditions, this device provided linear range at concentrations of 0.01–10 µg/mL for the detection of Nor and Enr and limit of detection was calculated as 2.02 and 1.70 ng/mL, respectively. Moreover, this device demonstrates performance comparable to standard methods for the simultaneous detection of Nor and Enr in milk, honey, and fish. Therefore, label-free electrochemical immunosensors provide a highly potent, inexpensive, and portable method for detecting multiple quinolone antibiotics simultaneously on a single device. [Display omitted] • Origami immunosensor was developed for simultaneous detection without labeling. • The oPAD can specifically analyze quinolone residues at the ng/mL level. • Norfloxacin and enrofloxacin in real food samples are accurately estimated. [ABSTRACT FROM AUTHOR]

This review proposes, for the first time, a recent overview of ecological information involving electrochemical paper-based analytical devices (ePADs) dedicated to sensing environmental and clinical situations. The options of manufacturing methods are screen printing, stencil printing, pencil drawing, laser scribing, inject-printing, and additive printing. We have covered ecological aspects such as resource efficiency, safety, and toxicity regarding using paper-based (bio) electrodes. To see the ecological impact of testing methods by using ePADs, the Analytical GREEnness (AGREE) approach was utilized as a greenness metric calculator model since the tool makes use of 12 principles of Green Analytical Chemistry. Positive and negative concepts from the revised values of AGREE metric of clinical and environmental analysis were introduced and discussed. Also, we finalize the present review informing the life cycle of ePAD and some challenges that can impact the next generation of disposable electrodes. • The greenness metrics involving paper-based electrochemical (bio)sensors have been reviewed. • Ecological impact for environmental and clinical analysis was introduced using the AGREE approach. • Resource efficiency, safety, and toxicity regarding using paper-based (bio)electrodes are discussed. • The life cycle and challenges that can impact the next generation of disposable electrodes are covered. [ABSTRACT FROM AUTHOR]

Developing disposable paper-based devices has positively impacted analytical science, particularly in developing countries. Some benefits of those devices include their versatility, affordability, environmentally friendly, and the possibility of being integrated with portable electrochemical or colorimetric detectors. Paper-based analytical devices (PADs) comprising circular zones and microfluidic networks have been successfully employed in the analytical chemistry reign. However, the combination of the stencil-printing method and alternative binder has not been satisfactorily explored for fabricating colorimetric paper devices. We developed PADs exploring the stencil printing approach and glass varnish as the hydrophobic chemical agent. As a proof-of-concept, the colorimetric assay of salivary α-amylase (sAA) was performed in saliva samples. Through the scanning electron microscopy measurements, it was possible to indicate satisfactory definitions between native fibers and barrier, and that the measured values for the channel width revealed suitable fidelity (R2 = 0.99) with the nominal widths (ranging from 400 to 5000 μm). The proposed hydrophobic barrier exhibited excellent chemical resistance. The analytical applicability for detecting sAA revealed linear behavior in the range from 2 to 12 U mL−1 (R2 = 0.99), limit of detection of 0.75 U mL−1, reproducibility (RSD ≤2.4%), recovery experiments ranged from 89 to 108% and AGREE response (0.86). In addition, the colorimetric analysis of sAA in four different saliva samples demonstrated levels ranging from 202 to 2080 U mL−1, which enabled monitoring the absence and presence of periodontitis. This report has presented the first use of a self-adhesive mask and glass varnish for creating circular zones and microfluidic architectures on paper without using thermic or UV curing treatments. Also, the proposed analytical methodology for detecting sAA exhibited suitable ecological impact considering the AGREE tool. We believe the proposed fabrication of paper devices emerges as a novel, simple, high-fidelity microfluidic channel and portable analytical approach for colorimetric sensing. [Display omitted] • Paper-based analytical devices (PADs) comprising circular zones and microfluidic networks have been manufactured. • The stencil printing approach and glass varnish as the hydrophobic agent were utilized. • The proposed hydrophobic barrier presented suitable chemical resistance. • Colorimetric detection of salivary α-amylase in saliva samples was performed. [ABSTRACT FROM AUTHOR]

• N-protein detection in saliva without any sample treatment. • No waste solution after the saliva analysis. • Miniaturised and easy-to-use disposable device. • Smartphone-assisted electrochemical immunosensor. Herein, we developed a new waste solution-free paper-based electrochemical immunosensor for SARS-CoV-2 detection in saliva, by combining vertical and lateral flow. In detail, the device was constituted of a reservoir containing all reagents for the construction of the immunological chain onto the magnetic beads and a lateral flow holder which contained a polyester-based electrode, a magnet, and an adsorbent pad. The measurement was carried out by adding the saliva sample into the reservoir, followed by the addition of this solution in the hole present in the lateral flow holder. The successive additions of washing buffer and TMB solution in the lateral flow holder allowed the detection of N protein in saliva in the range of 0.06 to 4 µg/mL with a detection limit equal to 30 ng/mL. The analysis of several saliva samples with the sensing tool and the reference method, demonstrated the effectiveness of this device, being able to identify positive patients with high values of CT e.g. 35. This new configuration paves the way for the realization of any magnetic beads-based immunosystem without waste solution production, enlarging the application of paper-based devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A laser-derived paper-based three electrode system was fabricated. • The electrodes were thoroughly characterized physically and electrochemically. • The multi-functional sensing ability of the fabricated electrodes was demonstrated. • The chemically engineered electrodes offered great reproducibility and reliability. • Real sample assessment included small molecules, free radicals, and macromolecules. The demand for eco-friendly, disposable, and affordable electrochemical sensors stimulates the fabrication of laser-directed paper-based electrodes. This work reports the fabrication of laser-derived patterns on the paper substrate and its multi-functional sensing applications. For this, a computer-aided design (CAD) software-driven computer numerical control (CNC) manufacturing method was developed to engrave a three-electrode design on a paper substrate. The fabricated L aser- D irected e lectrochemical P aper A nalytical D evice (LD-ePAD) was thoroughly characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle analysis, electrochemical impedance spectroscopy (EIS), and the cyclic voltammetry (CV). After that, we demonstrated the multi-functional sensing ability of the LD-ePADs by detecting diverse model analytes, including small molecules (i.e., lead ions [Pb2+]), free radicals (i.e., peroxide [H 2 O 2 ]), and macromolecules (i.e., Alkaline phosphatase [ALP]). Upon investigation, it exhibits a fair detection limit of 5.19 (±0.21) µM for Pb2+, 48.66 (±0.31) µM for H 2 O 2 , and 0.48 (±0.02) U/L for ALP. The LD-ePADs' outstanding repeatability, stability, abundance of catalytic active sites, remarkable tunability, and potential for nano-bioengineering emphasized their tremendous commercial feasibility. To the best of our knowledge, this is the first study to use controlled one-step laser direct engraving to fabricate a three-electrode setup on a paper-substrate that can sense three heterogeneous molecules electrochemically. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) currently remains a major life-threatening disease as it can be fatal if not treated properly or in a timely manner. Herein, we first describe a disposable and cost-effective paper-based electrochemical biosensor based on a gold particle-decorated carboxyl graphene (AuPs/GCOOH)-modified electrode for detecting heat shock protein (Hsp16.3), which is a specific biomarker indicating the onset of TB infection. The device pattern was first engineered to facilitate detection procedures and printed on low-cost filter paper to create hydrophobic and hydrophilic regions using a wax printing technique. Immunoassays proceeded in a half-sandwich format because it is a reagent-less approach and requires no labeling step. The fabrication of the immunosensor began with GCOOH drop casting, the electrochemical deposition of AuPs, and the establishment of a biorecognition layer against Hsp16.3 utilizing 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS)-sulfo standard chemistry. The appearance of Hsp16.3 resulted in a substantial decrease in the electrochemical signal response of the redox probe employed [Fe (CN) 6 ]3−/4− due to the created immunocomplexes that possess insulation properties. GCOOH enables direct antibody immobilization, and AuPs enhance the electrochemical properties of the sensor. This proposed immunosensor, while requiring only a miniscule sample volume (5 μL), achieved superior performance in terms of the limit of detection, measuring at 0.01 ng/mL. Our platform was confirmed to be highly specific to Hsp16.3 and can rapidly detect TB-infected sera without necessitating any pre-enrichment (20 min), making it an alternative and particularly suitable for the early diagnosis of TB in resource-scarce countries. [Display omitted] • An engineered paper-based electrochemical biosensor was first proposed for detection of Hsp 16.3 to diagnose TB infection early. • AuPs and GCOOH decorated on the working area enhanced the sensing capabilities of the established PAD. • Laten and active TB-infected human sera can be directly detected without requiring any pre-enrichment. • The established biosensor was sensitive, low-cost, portable, and disposable. [ABSTRACT FROM AUTHOR]

As a crucial biomarker for some diseases, the determination of cholesterol in human serum is of great significance for the diagnosis and prevention of these diseases. Hence, a portable cholesterol detection method is necessary for clinical and domestic applications. Here, a portable paper sensor was designed for cholesterol detection by modifying screen-printed electrode (SPE) with nanoporous gold (NPG). To achieve the reliable cholesterol detection, a synergistic strategy was proposed based on the oxidation of cholesterol by cholesterol oxidase (ChOx) and the reduction of oxidation product (H 2 O 2) by NPG. Compared to existing electrochemical sensors, the resulting paper sensor exhibited a wider linear response in a range from 50 μM to 6 mM as well as a higher sensitivity of 32.68 μA mM−1 cm−2 with a lower detection limit of 8.36 μM. Moreover, the portable paper sensor presented strong anti-interference capability and stability in the detection of cholesterol in human serum, and the data detected by the portable paper sensor were consistent with that obtained by an automatic biochemical analyzer. These unique performances confirmed that the proposed paper sensor was a sensitive, reliable, and portable cholesterol detection method, making it a good choice for cholesterol detection. [ABSTRACT FROM AUTHOR]

Point-of-care testing (POCT) technology is urgently required owing to the prevalence of the Internet of Things and portable electronics. In light of the attractive properties of low background and high sensitivity caused by the complete separation of excitation source and detection signal, the paper-based photoelectrochemical (PEC) sensors, featured with fast in analysis, disposable and environmental-friendly have become one of the most promising strategies in POCT. Therefore, in this review, the latest advances and principal issues in the design and fabrication of portable paper-based PEC sensors for POCT are systematically discussed. Primarily, the flexible electronic devices that can be constructed by paper and the reasons why they can be used in PEC sensors are expounded. Afterwards, the photosensitive materials involved in paper-based PEC sensor and the signal amplification strategies are emphatically introduced. Subsequently, the application of paper-based PEC sensors in medical diagnosis, environmental monitoring and food safety are further discussed. Finally, the main opportunities and challenges of paper-based PEC sensing platforms for POCT are briefly summarized. It provides a distinct perspective for researchers to construct paper-based PEC sensors with portable and cost-effective, hoping to enlighten the fast development of POCT soon after, as well as benefit human society. • The merits of functionalized paper for PEC sensor are introduced. • Photosensitive material and signal amplification strategy of paper-based PEC sensor are discussed. • The application of paper-based PEC sensor in the field of POCT is highlighted. • The limitations and challenges of paper-based PEC sensor are summarized. [ABSTRACT FROM AUTHOR]

Globe Thistles-Like NiCo 2 S 4 and rGO grow on flexible paper for the detection of H 2 O 2. [Display omitted] • To paper as the basement, successfully developed a low cost and biodegradable flexible electrochemical sensor electrode materials. • NiCo 2 S 4 microspheres with unique globe thistles-like structure was prepared for the first time. • The NiCo 2 S 4 /rGO/FP electrode has high sensitivity, low LOD, and wide linear range. The Globe Thistles-Like (GTL) NiCo 2 S 4 nanostructures were supported on reduced graphene oxide modified filter paper (FP). The prepared GTL NiCo 2 S 4 /rGO/FP is investigated as a disposable and flexible electrode for the electrochemical detection of H 2 O 2 in alkaline media. Owing to the rich redox active sites, the synergistic effect between Co3+ and Ni2+, and the rapid electron transportation of substituting sulfur (S) for oxygen (O) in NiCo 2 O 4 , the GTL NiCo 2 S 4 /rGO/FP exhibits considerable enzyme-free H 2 O 2 sensing performance with wide linear H 2 O 2 ranging from 38.8 to 37306.8 μM, high sensitivity of 2.4326 mA mM−1 cm−2, and low detection limit of 0.08 μM. The GTL NiCo 2 S 4 /rGO/FP electrode has stable sensing performance and is highly selective toward analyte for physiological interfering species. The excellent electrochemical performance of GTL NiCo 2 S 4 /rGO/FP composite is attributed to the GTL structure of NiCo 2 S 4. By studying the hydrothermal reaction time, electrochemical active surface area, and hydrophilic-hydrophobic surfaces of GTL NiCo 2 S 4 /rGO/FP composite, the relationship between the microstructure and sensing performance of the composite was elucidated. Surely this study opens up new possibilities for the application of low-cost, biodegradable flexible electrode materials in wearable sensors in the near future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Paper sensors allowed pesticide sensing on the skin of fruits and vegetables. • The wearable sensor activated in an acid medium exhibited better performance. • Excellent correlation of the sensor with a "gold standard" technique was obtained. Wearable sensors such as those made with paper are needed for non-destructive routine analysis of pesticides on plants, fruits, and vegetables. Herein we report on electrochemical sensors made with screen-printed carbon electrodes on kraft and parchment papers to detect the fungicide carbendazim. A systematic optimization was performed to find that electrochemical sensors on kraft paper treated in an acidic medium led to the highest performance, with a detection limit of 0.06 µM for carbendazim. The enhanced sensitivity for this sensor was attributed to the porous nature of kraft paper, which allowed for a large electrode surface area, and to the carboxylic groups formed during electrochemical activation. As a proof-of-concept, the electrochemical sensor attached to the skin of apple and cabbage was used to detect carbendazim with the same performance as the gold standard method, thus demonstrating that the sensor can be used in the farm and on supermarket shelves. [ABSTRACT FROM AUTHOR]

The remarkable features of a carbon fiber paper sensor (CP) were employed for detection of the estrogenic hormone 17α-ethinylestradiol (EE2), considered a contaminant of emerging concern due to its potential ecotoxicity and widespread in the aquatic ecosystems. In this work, an unpreceded CP pre-treatment study was conducted with the (Il)-hexacyanoferrate(III) ion pair, however a bare sensor without pre-treatment revealed higher efficiency on the oxidation of EE2 compared to a chemical and electrochemical pre-treated CP and a gold nanoparticles modified CP, being thus selected for EE2 determinations. The analytical conditions were thoroughly optimized in terms of electrolyte pH (pH 7), differential pulse voltammetry parameters (modulation time 0.003 s, amplitude 0.09 V, interval time 0.1 s and step potential 0.01 V), and analyte preconcentration potential (0.4 V) and time (180 s). The hormone can be determined by the CP in a wide linear range from 0.1 to 1000 nM, achieving a detection limit of 0.14 ± 0.005 nM and an outstanding sensitivity of 1636 ± 232 μA μM−1 cm−2 in the lowest linear zone (0.1–1 nM). The sensor was validated in river water and fish reaching good recoveries (91.2 ± 4.6 to 109.0 ± 7.1%), reproducibility and repeatability. Moreover, the sensor showed high selectivity to EE2 in the presence of several potential interfering compounds and frequently prescribed drugs, though it could not discriminate the similar hormone, 17β-estradiol, being the total concentration obtained in this case. CP-based sensors emerge as efficient electroanalytical tools, suggesting that modification of the surface may not always be beneficial in terms of sensitivity. [Display omitted] • A simple and effective carbon paper sensor was used for 17α-ethinylestradiol sensing. • The best analytical signal was obtained with an untreated and unmodified carbon paper. • The optimized sensor achieved high sensitivity (1636 μA μM−1 cm−2) and LOD of 0.14 nM. • Application in complex samples of fish resulted in recoveries from 102 to 109%. • Carbon paper sensors can be become valuable tools in the electroanalytical field. [ABSTRACT FROM AUTHOR]

In this work, electrodes based on laser-scribed reduced graphene oxide were fabricated using filter paper as the substrate. To fabricate the electrodes, a water suspension of graphene oxide was filtered to produce a continuous and uniform film of graphene oxide on the filter paper surface. Subsequently, a CO 2 laser was used to "write" the working, counter and reference eelctroes by reducing graphene oxide in specific areas to define complete sensors. Referecnce electrodes were then coated with a commercial Ag/AgCl conductive paste to produce a quasi Ag/AgCl reference. As fabricated devices were employed as electrochemical sensors for detection of phosphate ions in water by employing the molybdenum blue method. This method exploits the reaction between molybdate and phosphate ions in acidic media leading to a Keggin-type complex (P M o 12 O 40 3 − ) which, being electrochemically active, enables the indiret detection of phosphate ions. Sensors exhibited high selectivity and sensitive detection of phosphate ions in a wide linear range, from 1 to 20 µM; with a limit of detection of 0.4 µM. To demonstrate that sensors could be utilized for in-situ phosphate ion detection, paper substrate was first pre-loaded with sulphuric acid and molybdate ions. During analysis, these chemicals were then desorbed directly into the test sample eliminating the need for any kind of external manipulation or reagent addition. Thus, this paper presents the fabrication of a portable, easy-to-use, biodegradable and fast phosphate ions sensor for in situ and real-time monitoring of water quality. [ABSTRACT FROM AUTHOR]

Cd2+ and Pb2+ are two typical metallic pollutants in food. Therefore, it is of great significance to establish a method which can simultaneously detect them. Here, an electrochemical sensor was established to simultaneously detect Cd2+ and Pb2+ in food samples based on sensing electrode prepared by conductive carbon paper, rGO and CoZn·MOF (CP-rGO-CoZn·MOF). Under the optimized conditions, the proposed electrochemical sensor achieves simultaneous detection of Cd2+ and Pb2+ low to 0.565 nM (Cd2+) and 0.588 nM (Pb2+), respectively. Further selective experiments and repetitive experiments perform well. Spiked experiments find that the recovery rates of Cd2+ and Pb2+ in food samples are between 97.5% to 105.9% and 94.3%–109.6%, indicating the established electrochemical sensor owns a good response to the targets. Besides, relative standard deviations (RSD) of them are no more than 5.817%, showing its potential in practical applications. [Display omitted] • Constructing electrode large surface area, and good electrical conductivity based on bimetallic MOF and CP-rGO. • CP-rGO-CoZn·MOF electrode is used for the detection of Cd2+ and/or Pb2+ for the first time. • Simultaneous detection of Cd2+ and Pb2+ low to 0.565 nM (Cd2+) and 0.588 nM (Pb2+). • Constructing a portable electrochemical sensor with good stability. [ABSTRACT FROM AUTHOR]

As a β-stimulant, clenbuterol (CLB) is abused to varying degrees by athletes worldwide. It is also used in the meat and dairy industries. CLB inadvertently enters the human body through the food chain, endangering human health. Therefore, a rapid and convenient method for detecting CLB is needed. In this study, nanocarbon-supported NiFe 2 O 4 electrode materials (NiFe 2 O 4 –NPCs) were synthesized, and an electrochemical sensor (NiFe 2 O 4 –NPCs/GCE) for CLB detection was fabricated. NiFe 2 O 4 –NPCs have good electrical conductivity, electrocatalytic activity, and high electrical flux, owing to their large specific surface area and the anti-spinel structure of NiFe 2 O 4. The fabricated sensor is an effective detector of CLB. The sensor exhibits linear ranges of 10−7–10−5 M and 7 × 10−11–10−7 M and a limit of detection (LOD) of 3.03 × 10−12 M (S/N = 3). The sensor also exhibits good sensitivities of 3.264 μA μM−1 cm−2 and 0.751 μA μM−1 cm−2 (S/N = 3). Additionally, NiFe 2 O 4 –NPCs/GCE successfully detected CLB in real samples of human urine. Thus, this study highlights the potential of the NiFe 2 O 4 –NPCs/GCE sensor for the detection of CLB in biological samples. [Display omitted] • Synthesized a nanocarbon-supported NiFe 2 O 4 electrode material for the detection of clenbuterol (CLB). • Innovative approach for overcoming the low electrochemical ability of CLB. • Successfully used for the detection of CLB in real samples of human urine. [ABSTRACT FROM AUTHOR]

We developed an electrochemical paper-based device (ePAD) for the online separation and simultaneous determination of structurally similar carbofuran (CBF) and carbaryl (CBR). Our device combined paper chromatography and an electrochemical sensor as a single system for increasing the selectivity to simultaneous detection of the two pesticides. During the simultaneous detection of CBF and CBR, the separation of the two carbamate compounds depends on the differences between the movements of the substances on the chromatographic paper in the moving phase flow. The isolated pesticides were electrochemically measured using an amperometric method. Under optimal conditions, which include the effect of the mobile phase, separation channel, and the applied potential, the proposed device provides a linear range for the simultaneous determination of CBF and CBR from 0.1 to 2.0 and 0.5–7.5 mg L−1, with the limits of detection at 0.06 and 0.40 mg L−1, respectively. Furthermore, we successfully used the developed device to determine CBF and CBR in water, cucumber, and cabbage samples. The obtained results correspond to results obtained from a standard method. This developed ePAD is low-cost and uses a low sample volume (2 µL). Moreover, it is disposable, portable, and a promising tool for the on-site quantification of pesticides in actual samples. • Paper chromatography integrated with electrochemical detection (ePAD) is highlighted. • A separation-based ePAD was first developed for detection of CBF and CBR pesticides. • Online separation and simultaneous detection of structurally similar compound were achieved. • The ePAD provides highly selective and sensitive detection of CBF and CBR. • This sensor was successfully applied to determine CBF and CBR in real samples. [ABSTRACT FROM AUTHOR]

Early identification of ovarian cancer improves treatment options & survival rates. An electrochemical paper analytical device (ePAD) was reported in this study for detecting Platelet-derived growth factor (PDGF), an ovarian cancer biomarker. This research aims to create a quick nano-biosensing approach to recognize deadly ovarian cancer (OC) at an initial phase. The suggested ePAD has numerous positive characteristics, including simple, low-cost, repeatable, & disposable. The ePAD's working electrode contains silver nanoparticles. Furthermore, aptamers have improved the biosensor's functionality. Transmission electron microscopy (TEM), FTIR analysis, X-ray diffraction (XRD), UV–vis spectroscopy, & Zeta potential test were utilized to evaluate the silver nanoparticles' morphological, optical, elemental content, and phase analyses. This aptamer-modified ePAD helps amplify the designed platform's signal to detect PDGF. The interaction of aptamer & PDGF was discovered by lowering the current created by the contact with methylene blue (MB), an anionic indicator. The designed sensor demonstrated an optimum response & broad linearity of 0.01–10.0 μg/ml for PDGF, with 0.01 μg/ml of limit of detection (LOD). [Display omitted] • The developed sensor showed good sensitivity as well as reproducibility. • A chemically synthesized and very well characterized silver-based nanoparticles were utilized. • Cross-reactivity was confirmed by utilizing Urea. • The constructed electrochemical sensor worked efficiently in artificial serum. • This sensor could be used for detecting ovarian cancer biomarker. [ABSTRACT FROM AUTHOR]

In this study, we present for the first time a simple and novel method for the fabrication of paper-based electrochemical sensors. The device development was carried out in a single stage with a standard wax printer. Hydrophobic zones were delimited with commercial solid ink, while electrodes were generated using new composite solid inks of graphene oxide/graphite/beeswax (GO/GRA/beeswax) and graphite/beeswax (GRA/beeswax). Subsequently, the electrodes were electrochemically activated by applying an overpotential. Various experimental variables for the GO/GRA/beeswax composite synthesis and electrochemical system obtention were evaluated. The activation process was examined by SEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurement. These studies showed morphological and chemical changes in the electrode active surface. As a result, the activation stage considerably improved the electron transfer on the electrode. The manufactured device was successfully applied for galactose (Gal) determination. This method presented a linear relation in the Gal concentration range from 84 to 1736 μmol L−1, with a LOD of 0.1 μmol L−1. The variation within and between-assay coefficients were 5.3% and 6.8%, respectively. The strategy here exposed for paper-based electrochemical sensors design is an unprecedented alternative system and represents a promising tool for mass production of economic analytical devices. A paper-based solid ink sensor construction for biosensor fabrication. [Display omitted] • Development of new composite solid inks based on graphite and beeswax. • Successful fabrication of paper-based electrochemical sensors. • Application of the developed device evaluated in the determination of galactose. [ABSTRACT FROM AUTHOR]

Carbon cloth and carbon paper have unique characteristics such as conductivity, mechanical strength, porosity, reduced dimensions, and adjustable size and shape. With these materials, different simple modification strategies can be employed, with emphasis on the direct growth of metal-based catalysts through single-step hydrothermal methods. Thus, owing to these interesting features, highly efficient, versatile, and disposable electrochemical (bio)sensors based on carbon cloth and carbon paper have been designed for biomolecules, biomarkers, and hazardous and chemical compounds detection in clinical, environmental and food samples, as well as in industrial products. Moreover, the advantage of facile integration in miniaturized and portable devices, envisages their successful application in point-of-care diagnostics and in-situ measurements. Therefore, this review highlights the main advances and the current research gaps concerning the design of these novel electroanalytical tools. • CC and CP present high electrical conductivity, porosity, and adjustable size/shape. • Single-step hydrothermal methods are the most used for CC and CP modification. • CC and CP (bio)sensors successfully used in clinical, environmental and food analysis. • Excellent performance of CP and CC (bio)sensors reaching sub-micromolar levels of LOD. • Facile integration in miniaturized and portable devices for in-situ measurements. [ABSTRACT FROM AUTHOR]

Cannabis smoking is on the rise as a result of cannabis legalization across the world. The intake of cannabis by smoking has an impact on the mental health of smokers and intimates. Therefore, rapid monitoring of illicit cannabis use via direct saliva samples is necessary. The Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and thiocyanate (SCN) level in saliva can be an effective biomarker to differentiate between cannabis and non-cannabis smokers such as cannabis ingestion, cigarette smokers, and healthy people. In this work, there is a development of an electrochemical sensor, "copper-phthalocyanine-modified screen-printed graphene electrodes (CuPc/SPGE)," for the concurrent determination of Δ⁹-THC and SCN using differential pulse voltammetry. Furthermore, the applicability of the CuPc/SPGE sensor was verified by simultaneously measuring Δ⁹-THC and SCN in saliva samples. The results from the developed sensor were similar to those obtained by high-performance liquid chromatography. This proposed sensor represents a first step in the differentiation of illegal cannabis smokers using the correlation between the contents of Δ⁹-THC and SCN in saliva, with features of rapidity, simplicity, low cost, and disposability. [Display omitted] • The simultaneous detection of Δ⁹-THC and SCN was first proposed to differentiate cannabis smokers and non-cannabis smokers. • The CuPc/SPGE can enhance the sensitive concurrent detection of Δ⁹- THC and SCN. • The surfactant system was also used to improve the solubility of Δ⁹-THC in the electrolyte phase. • The proposed sensor has been achieved for Δ⁹-THC and SCN determination in saliva samples with high accuracy. [ABSTRACT FROM AUTHOR]

Conventional airborne virus measurement usually requires appreciable sampling and detection times. Viral aerosols should also be collected or prepared in a liquid medium whose volume typically ranges from milliliters to tens of milliliters; hence, many sampling and detection steps need to be taken with the unit horizontal or immobile. Moreover, viral aerosols need to be sufficiently enriched, which makes real-time monitoring difficult. Herein, we present a near real-time enrichment and quantification system of airborne viruses that consists of a wet-paper-based electrochemical immunosensor with a gel electrolyte and a modified electrostatic particle concentrator. A small amount of phosphate-buffered saline flowed on the electrode, which resulted in sensor electrodes that are barely wet (covered in a thin buffer film measuring several micrometers) to ensure antigen–antibody interaction and the removal of non-target particles on the electrode surface. This system ensures that airborne viruses are highly enriched on the working electrode of the immunosensor, and it is possible to measure the MS2 virus particle concentrations every 10 min for 60 min stably and selectively against non-target airborne viruses and bacteria at horizontal and tilted measurement configurations. This system thus has the potential to be used in the real-time mobile monitoring of airborne microorganisms. [Display omitted] • Wet-paper-based electrochemical immunosensor under an electrostatic field is used to sample and quantify airborne viruses. • The sensors are barely wet to ensure antigen-antibody interaction and the removal of non-targets. • The enrichment ratio for airborne viruses is very high (> 108). • Airborne viruses are sampled and stably measured every 10 min for 60 min. • Airborne viruses are measured selectively against non-targets even when the unit is tilted. [ABSTRACT FROM AUTHOR]

• Carbon fiber-supported Cu 2 O NPs is prepared by a cyclic redox treatment. • Hydroxyl adsorption derived reactive oxygen promotes Cu 2 O NPs activity. • We speculate that glucose oxidation and reactive oxygen process are complementary and mutually reinforcing. • The detection range of the Cu 2 ONPs was 0.05 mM − 3 mM with a sensitivity of 3 mA mM−1 cm−2. Engineered sensitive copper nanostructured superelectrode systems have become an important part of electrochemical sensing of glucose because of their high sensitivity, specificity, abundant natural reserves, and environmental friendliness. However, the factors affecting the electrochemical catalytic activity of glucose remain a challenging issue, which largely limits the overall electrochemical sensing performance of glucose. This paper reports the design of a carbon fiber loaded cuprous oxide nanoparticle (Cu 2 O NPs) electrochemical sensor with electrochemical catalytic properties for glucose oxidation. The copper grown on carbon nanofibers was subjected to cyclic redox treatment to obtain Cu 2 ONPs with good glucose detection ability. The detection range of the prepared Cu 2 ONPs was 0.05 mM − 3 mM with a sensitivity of 3 mA mM−1 cm−2. The differences in the properties of copper and cuprous oxide are analyzed in depth and the reasons for the variability are explored. By observing the electrocatalytic behavior and oxygen evolution reaction behavior of the glucose oxidation process, we hypothesized that the difference in the oxygen source provided by hydroxyl adsorption would lead to the difference in the properties of cuprous oxide and copper. Our proposed differences in the oxygen source generated by hydroxyl adsorption affecting the performance of glucose detection will provide new ideas for the design of glucose electrochemical microelectrodes. [ABSTRACT FROM AUTHOR]

This study describes the development of electrochemical paper-based analytical devices (ePADs) using carbon-based paste combining silicone glue and graphite powder. The ePADs were manufactured using the screen-printing technique, which consisted of depositing the conductive ink on a screencast on the paper surface. In addition, an alternative electrical connector was designed and 3D-printed to make the detection method cheaper, portable and reproducible. The morphological, structural, and electrochemical properties of the conductive material developed were investigated through scanning electron microscopy (SEM), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements. The ePADs combined with the alternative connector revealed high repeatability, reproducibility, and stable responses considering a well-known redox probe ([Fe(CN) 6 ]4-/3-). In addition, the proposed ePAD provided a linear response for standard solutions of ascorbic acid (AA) in the concentration range between 0.1 and 2.0 mmol L−1. The achieved limit of detection was 4.0 μmol L−1. As proof of applicability, the ePADs were evaluated for AA analysis in synthetic biofluids (blood plasma and urine), vitamin C tablets, and food (gelatine and orange juice) samples. The analytical parameters of the proposed device were compared with other reports in the literature and exhibited similar or even superior performance, highlighting its feasibility for sensing applications. [Display omitted] • A carbon-based ink prepared by mixing graphite powder and silicone glue was used to develop screen-printed electrodes on paper. • An inexpensive 3D printed holder ensured simple assembling and suitable reproducibility. • Paper-based sensors revealed great stability and analytical performance. • Ascorbic acid was successfully determined in different samples. [ABSTRACT FROM AUTHOR]

• Electrochemically modified graphite paper is used as electrode substrate. • Molecular interactions of 3-MCPD on polymer was computationally analyzed. • The sensor surface shows a uniform coating Pt@PB Nanoparticles. • MIP/Pt@PB/EM-GP has important application prospects in future detection research. In this study, a molecularly imprinted polymer (MIP) electrochemical sensor based on electrochemically modified graphite paper (EM-GP) was developed for the detection of 3-MCPD for the first time. To this end, Prussian blue (PB) was electrodeposited on EM-GP to yield uniformly distributed PtNPs. The successful preparation of Pt@PB/EM-GP was verified by SEM, Raman spectroscopy, XRD, XPS, and EDS. MIP was then prepared by CV electropolymerization with template molecules (3-MCPD), and density functional theory (DFT) at M06-2X/6–31 + g (d,p) level was used to calculate the molecular-level interaction between 3-MCPD and MIP. Under the optimum conditions, the dynamic linear range of the sensing platform varied from 1 × 10-8 mol/L to 5 × 10-5 mol/L with a detection limit estimated to 5 × 10-9 mol/L (S/N = 3). Overall, these findings look promising for the construction of selective and quick detection platforms of 3-MCPD in food samples. [ABSTRACT FROM AUTHOR]

Topical lidocaine patches are commonly used to relieve pain and suffering in various clinical and household settings. Despite its extensive use, excessive skin absorption during numbing or pain reduction procedures can cause systemic toxicity, which can lead to life-threatening conditions. Rapid and reliable monitoring of escalating levels of lidocaine in the blood could help management/prevention of lidocaine overdose and its associated complications. To address this need, here we have developed a disposable point-of-care (POC) diagnostic platform composed of an integrated graphene-based electrochemical sensor with paper-based microfluidics for rapid detection of lidocaine levels in serum and blood samples. The fabrication process takes advantage of advanced, scalable manufacturing techniques, including printing, laser processing, and nondestructive near infrared (NIR) drying. The sensitivity tests of the platform revealed a sensitivity of ∼0.2 μA μM−1 towards lidocaine concentrations in the clinically relevant range (1–100 μM) in both complex matrix fluids of serum and blood with high cross specificity in the presence of the interfering analytes. This proof-of-concept platform could be regarded as the first step toward the development of low-cost and translational POC devices that could help in better pain management and reduce potential side effects or misuse of analgesics. [Display omitted] • Electrochemical detection of lidocaine using printed graphene electrodes. • NIR cured graphene electrodes achieved fast processing and higher sensitivity of ∼0.2 μA μM−1. • The manufacturing process takes advantage of the printing and laser cutting for scalable and cost-effective production. • The platform shows high selectivity towards lidocaine with similar detection performance in both serum and blood. [ABSTRACT FROM AUTHOR]

• A cheap, disposable, biodegradable and fast electrochemical paper-based device (ePAD) for exosomes determination was designed. • Preparation of mesoporous carbon foam with a lot of pores without using a template. • An ePAD contains the synthetic carbon and silver ink screen printed on the paper modified with AuNPs@MCF/MWCNTs ternary nanocomposite. • The low detection limit, high sensitivity and selectivity were obtained. Mesoporous carbon as a new class of three-dimensional conductive carbon materials has attracted more attention due to its significant surface area, unique flexibility, and lots of porosity. In this paper, a cost-effective, biodegradable electrochemical sensor was fabricated based on a highly flexible chromatographic paper with a lab-made carbon ink. The electrochemical response was enhanced with mesoporous carbon functionalized with multi-carbon nanotubes and gold nanoparticles (AuNPs@MCF/MWCNTs). Then, the CD9 antibodies were immobilized on the porous surface of the nanocomposite to combine with proteins overexpressed on the exosomal membrane. This structure and electrostatic repulsion effectively protect the electron transfer of the redox probe and lead to quantitative detection of exosomes using changes in the current. This paper-based immunosensor revealed a high sensitivity (the very low detection limit of 70 exosomes/µL and a linear range of 1 × 102 to 1 × 107 exosomes/µL) and suitable selectivity for detection of exosomes in the plasma sample. This paper-based immunosensor can prepare a clear horizon for using this kind of biosensors in the early detection and screening of diseases such as cancers in miniaturization and accessible system, especially Point of Care Testing (POCT) devices. [ABSTRACT FROM AUTHOR]

Herein, we report the development of a simple green methodology to fabricate N-doped carbon quantum dots (N-CQDs) with a high luminescence using R. graveolens leaves following the hydrothermal method. Optical, chemical, morphological, and electrochemical properties were thoroughly investigated employing a variety of analytical techniques. The fabricated N-CQDs have a spherical shape, with an average diameter of 4.5 nm. Excitation dependent emission behaviour, 18% QY and green fluorescence were all observed in the N-CQDs. They are particularly resistant to various impacts such as ionic strength, pH, continuous visible light irradiation, and storage time. Since Cr(VI) ions are highly carcinogenic and mutagenic, there is an urgent demand for sensitive, selective, and efficient sensors for monitoring and measuring the amount of Cr(VI) ion in water in the environment. Hence, we developed the prepared N-CQDs as a label-free fluorescence and electrochemical probe for detecting Cr(VI) ions selectively and sensitively in aqueous solutions. Relying on static quenching together with the inner filter effect, N-CQDs performed exceptionally well as fluorescence sensors for Cr(VI) ions. The N-CQDs exhibit a limit of detection of 300 and 5 nM in the photoluminescence and differential pulse voltammetry analysis, respectively. The detection of Cr(VI) ions in real water samples using the developed sensor through both methods presented high precision without any interference. In addition, we also developed paper sensing strips for field application by depositing N-CQD on filter paper, which has been satisfactorily evaluated for sensing Cr(VI) in solid-state and solution mediums. [Display omitted] • Facile and green synthesis of N-CQDs from Ruta graveolens leaves with a QY of 18%. • Behave as an effective fluorescent sensor for Cr(VI) ions with the LOD of 300 nM. • Acts as an electrochemical sensor for Cr(VI) ion with a LOD of 5 nM. • Fluorescent paper strips were fabricated to detect Cr(VI) ions easily and rapidly. • The dual sensor exhibits excellent detection ability in real sample analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D paper-based microfluidic electrochemical device (3D-ePAD) was constructed. • Graphite-supported gold nanoparticles modified electrode was used as a working electrode. • Low-cost, disposable, simple, and miniaturized 3D-ePAD was performed for determination of GA in tea samples. The combination of µPAD with electrochemical transducers has gained advantages of miniaturization, high sensitivity, selectivity, simplicity of instrumentation, portability, rapid analysis, and so on. In this work, the development of a 3D paper-based microfluidic electrochemical device (3D-ePAD) for the determination of gallic acid (GA) was presented. The 3D-ePAD is composed of three electrodes (working, reference, and counter electrodes) in which the hydrophilic area of the working electrode was manually screen-printed and modified with graphite-supported AuNPs(AuNPs/C) ink. The evaluation of the electrochemical oxidation process of GA at modified and unmodified electrodes at 3D-ePAD indicated the improvement of anodic current responses at the AuNPs/C modified electrode which can be attributed to the intermolecular hydrogen-bonded network between AuNPs and GA. For quantitative determination of GA, the amperometric experiments were investigated under optimal conditions in which a linear relationship between the GA concentration and the recorded current was achieved. The sensor displays a good linear range of 1.0 to 100.0 μM and 0.1 to 2.0 mM for GA determination. The limit of detection (LOD) of 0.89 μM was achieved for GA by 3D-ePAD. Conclusively, the 3D-ePAD was performed successfully for the determination of GA in tea samples. [ABSTRACT FROM AUTHOR]

A paper-based surface-enhanced Raman scattering (SERS) sensor that combined the excellent performance of three-dimensional (3D) dendritic gold (DAu) matrix and the selective adsorption ability of biomimetic recognition polymer (BRP) has been constructed for ultrasensitive detection of thiram. The 3D DAu structure decorated on cellulosic matrix provides predominant SERS performance and chemical stability for the analytical platform. Compared with two-dimensional (2D) SERS platforms, it can get efficient utilization of 3D laser excitation volume to achieve optimal SERS enhancement. BRP membranes for the specific recognition and enrichment of thiram were prepared by bulk polymerization. And the urchin-like nanoparticles (UNPs) with rich cutting-edge structure were decorated in the BRP to provide sufficient "hot spots". In the region where DAU was close to UNPS, the synergistic SERS enhancement was generated through particle plasmon coupling. And the whole structure of the composite multilayer provides multiple SERS enhancement for thiram detection. The SERS response of the sensor toward thiram showed excellent correlation during the range of 1 × 10−10 to 1 × 10−7 mol·L−1 with the detection limits as low as 2.75 × 10−11 mol·L−1. The test results of selectivity, reproducibility, and accuracy indicated that the paper-based DAu/BRP (UNPs) sensor possessed potential applications in pesticides analytical and other related fields. • A three-dimensional SERS sensor was developed for pesticide residue detection. • The innovative preparation of dendritic gold matrix. • A reusable SERS paper slip which with multiple signal amplification strategies. [ABSTRACT FROM AUTHOR]

Carbon materials are widely used as electrodes because their versatility allows the manufacture of different electrochemical sensors. Chemical vapor deposition (CVD) is a versatile route for their production, allowing carbon growth on different substrates, such as ceramic fiber paper (CFP), a flexible and easy-to-handle material composed of alumina, silica, inorganic binders, and organic residues. Here, we demonstrate a route for carbon electrode preparation over CFP using methane as an additional carbon source to improve the electronic properties of the material. Different synthesis temperatures were tested, and the sample produced at 1000 °C (CFP-1000) was electrically conductive. The new material was applied as an electrochemical sensor to determine paracetamol in drugs, tap water, and synthetic urine samples using differential pulse voltammetry (DPV) and diquat in tap water and wild honey samples by the square-wave voltammetry (SWV) technique. For both, it was observed that the matrix effects were insignificant for the sensor. The limit of detection (LOD) calculated for paracetamol was 0.05 μmol L−1, while the LOD for diquat was 0.001 μmol L−1. [Display omitted] • A carbon-based electrode was produced by the CVD method over ceramic fiber paper. • Methane gas improved the ceramic fiber paper's electrical conductivity. • The electrode performed the paracetamol and diquat detection satisfactorily. • The sensor presented reproducibility and low LOD for paracetamol and diquat. [ABSTRACT FROM AUTHOR]

Bacillus anthracis is a fatal biological warfare agent, with a mortality rate of almost 100% when the bacteria are inhaled. Therefore, developing a biosensor for rapidly detecting B. anthracis spores in the ambient air is critical. Conventional techniques tend to be time-consuming, labor-intensive, and require highly trained personnel, thereby preventing rapid onsite detection. Moreover, low-cost, stable probes are required for continuous monitoring of multiple airborne targets. This study presents a paper-based electrochemical peptide sensor for rapid, label-free, sensitive, and economical quantification of liquid-borne and airborne Bacillus subtilis spores, widely used nonpathogenic B. anthracis simulant spores. These sensors were fabricated using wax printing on Whatman filter paper along with stencil-printed carbon paste electrodes and Ag/AgCl ink, as well as subsequent peptide (NHFLPKV) immobilization. These low-cost quickly fabricated sensors were characterized by differential pulse voltammetry and could detect spore concentrations as low as 6.9 × 102 colony-forming units (CFU) mL-1 in 30 min with high specificity towards the spores and stability. Furthermore, spore concentrations were determined from air samples obtained using the BioSampler, which demonstrated that these measurements agreed with those using the plate-counting assay; therefore, the surface proteins of the spores were intact through sampling with the BioSampler. These paper-based peptide sensors can be used for onsite rapid and continuous airborne spore-monitoring systems. • The first study to use a peptide-immobilized electrochemical paper-based sensor for detection of whole bacteria. • Rapid, label-free, sensitive, and economical quantification of airborne B. subtilis spores is presented. • The sensors detected spore concentrations as low as 6.9 × 102 CFU/mL in 30 min with low-cost and fast fabrication. • Measurements of air-sampled spores agreed with those using the plate-counting assay. • The surface proteins of the spores were intact through sampling with the BioSampler. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles were employed as signal amplification for detection of Sudan I. • Graphene oxide as flexible substrate was used to construct disposable electrode. • As-constructed paper-based electrode exhibited high sensitivity and selective for Sudan I detection in chili powder. In this study, a high-performance flexible reduced graphene oxide (rGO) paper electrode composed of silver nanoparticles (Ag NPs) for the detection of Sudan I was fabricated. Ag NPs were doped with rGO nanoheets by self-assemble and assembled into a paper electrode with layer-by-layer structure via vacuum filtration. Thanks to the highly efficient electrocatalysis of Ag NPs towards reduction of azo bond, the as-prepared hybrid paper can be used alone as a flexible sensor for the detection of Sudan I in chili powder, with the high sensitivity (22.93 μA μmol/L) and the low detection limit (41.3 nmol/L). The sensor also expressed good selectivity, repeatability, reproducibility, stability and recovery between 96.1% and 101.8% (RSD < 6%). With the advantages of low-cost and scalable production capacity, such Ag NPs/rGO functional papers can be used as flexible disposable sensors for electrochemical detection of Sudan I. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) cell culture system, as an alternative approach for traditional cell culture, attracts great attention because of physiological relevance and great microenvironment similarity to human conditions. Herein, a facile paper-polylactic (PLA) platform that was fabricated by wax printing and 3D printing, coupled with electrochemical sensor, was designed for the construction and intervention of 3D cell damage model. Pheochromocytoma cells (PC12) and bone marrow mesenchymal stem cells (BMSCs) were seeded on the paper-PLA 3D platforms and displayed the features of uniform distribution, good adhesion and perfect proliferation, as well as decreased circularity when compared to those grown on the two-dimensional (2D) interfaces. The electrochemical sensors revealed cell viability by monitoring dopamine released by cell models, ascertaining the applicability of the paper-PLA platform to a long-term 3D cell culture and drug assessment. Additionally, the results revealed that donepezil and BMSCs-secreted active molecules exhibited stronger cytoprotective effect against amyloid-beta oligomers-induced cell damage on the paper-PLA 3D printed platforms, indicating the cell damage model and the cell intervention model were achieved successfully in the simulated in vivo physiological microenvironment. Thus, the proposed paper-PLA platform may serve as a promising candidate for efficient drug screening and toxicity evaluation due to its simple structure, low cost, and convenient integration of 3D cell culture and activity evaluation. [Display omitted] • The PC12 cells and MSCs encapsulated in agarose gel were proliferated on the facile paper-PLA 3D printed platform. • Cell viability of different cell models was evaluated by paper-PLA 3D printed device combined with electrochemical sensor. • The type of paper may affect the activity of key small molecules secreted by BMSCs. • The facile paper-PLA 3D printed platform offers an ideal 3D cell culture product for drug screening and toxicity evaluation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ink-Jetted Miniaturized paper based electroanalytical device was fabricated. • ZnO nanoparticles were drop casted to modify the working electrode. • A linear range of 4 μM to 60 μM was found. • A 4.04 μM of limit of detection was within in the safe limit. • The device was tested for picric acid sensing in tap and lake water. Picric acid (PA) is one of the essential components utilized in manufacturing of explosives. Therefore, the detection of trace amount of PA is critical in forensic science, criminal investigation, military security and environmental safety. Owing to these attributes, development of a simple, rapid and point-of-care (POC) analytical method for PA detection and quantification is crucial. Herein, a low-cost, POC, ink jetted paper device has been developed for electroanalytical detection of PA. Inkjet printing is an economic fabrication process used for extruding several nanomaterials with diversified applications. By improving the ink viscosity, inkjet printers can simplify the fabrication of paper-based electrochemical sensor, and provide easy, fast, environmental friendly and viable for large scale production sensors, thereby adding its commercialization potential. In this work, a commercially available circuit board printer and an inexpensive high viscosity carbon conductive ink were used to print an electrochemical paper device. The fabricated device was used for electrochemical detection of PA using cyclic voltammetry (CV) and wave voltammetry (SWV). Various parameters like effect of potential scan rate from 10 mVs−1 to 300 mVs−1, effect of variable PA concentration effect was studied. A linear concentration range of 4 μM to 60 μM was obtained. For a working electrode of 7 mm2 surface area, the limit of detection (LOD) was 4.04 μM (922.56 ppb) which was less than the prescribed safe limit of 8 μM. Effect of interference with other chemicals was examined using SWV with the co-existing metals like zinc, lead, copper and mercury. Finally, real sample analysis for tap and lake water was successfully performed with the device. The developed cost-effective paper-based ink-jetted platform, with further fine-tuning and surface modifications, can be used for sensing various analytes as a point-of-care device. [ABSTRACT FROM AUTHOR]

Botulinum neurotoxins (BoNTs) produced by soil bacterium Clostridium botulinum are cause of botulism and listed as biohazard agents, thus rapid screening assays are needed for taking the correct countermeasures in a timely fashion. The gold standard method relies on the mouse lethality assay with a lengthy analysis time, i.e., 2–5 days, hindering the prompt management of food safety and medical diagnosis. Herein, we propose the first paper-based antibody-free sensor for reliable and rapid detection of BoNT/A and BoNT/C, exploiting their cleavage capability toward a synthetic peptide able to mimic the natural substrate SNAP-25. The peptide is labelled with the electroactive molecule methylene blue and immobilized on the paper-based electrode modified with gold nanoparticles. Because BoNT/A and BoNT/C can cleave the peptide with the removal of methylene blue from electrode surface, the presence of these neurotoxins in the sample leads to a signal decrease proportional to BoNT amount. The biosensor developed with the selected peptide and combined with smartphone assisted potentiostat is able to detect both BoNT/A and BoNT/C with a linearity up to 1 nM and a detection limit equal to 10 pM. The applicability of this biosensor was evaluated with spiked samples of orange juice, obtaining recovery values equal to 104 ± 6% and 98 ± 9% for 1 nM and 0.5 nM of BoNT/A, respectively. [Display omitted] • Smart electrochemical device for detection of BoNT/A and BoNT/C. • Detection of proteolytic activity of BoNTs against the synthetized peptide. • Electrochemical paper-based sensor combined with a smartphone-assisted device. [ABSTRACT FROM AUTHOR]

• Paper-based electrochemical sensors for hydrogen peroxide in aerosol phase. • Filter screen-printed electrode modified via drop casting with nanocomposite. • Electrochemical smartphone-assisted device to customize the disinfection process. The outbreak of COVID-19 is caused by high contagiousness and rapid spread of SARS-CoV-2 virus between people when an infected person is in close contact with another one. In this overall scenario, the disinfection processes have been largely improved. For instance, some countries have approved no-touch technologies by vaporizing disinfectants such as hydrogen peroxide, with the overriding goal to boost the safety of the places. In the era of sustainability, we designed an electrochemical paper-based device for the assessment of hydrogen peroxide nebulized by a cost-effective ultrasonic aroma diffuser. The paper-based sensor was fabricated by modifying via drop-casting a filter paper-based screen-printed electrode with a dispersion of carbon black-Prussian Blue nanocomposite, to assess the detection of hydrogen peroxide at −0.05 V vs Ag/AgCl. The use of paper-based modified screen-printed electrode loaded with phosphate buffer allowed for monitoring the concentration of hydrogen peroxide in aerosol, without any additional sampling instrument to capture the nebulized solution of hydrogen peroxide at a concentration up to 7% w/w. Hydrogen peroxide, a reconverted ultrasonic aroma diffuser, and the paper-based electrochemical sensor assisted by smartphone have demonstrated how different low-cost technologies are able to supply an useful and cost-effective solution for disinfection procedures. [ABSTRACT FROM AUTHOR]

Plant health monitoring is devised as a new concept to elucidate in situ physiological processes. The need for increased food production to nourish the growing global population is inconsistent with the dramatic impact of climate change, which hinders crop health and exacerbates plant stress. In this context, wearable sensors play a crucial role in assessing plant stress. Herein, we present a low-cost 3D-printed hollow microneedle array (HMA) patch as a sampling device coupled with biosensors based on screen-printing technology, leading to affordable analysis of biomarkers in the plant fluid of a leaf. First, a refinement of the 3D-printing method showed a tip diameter of 25.9 ± 3.7 μm with a side hole diameter on the microneedle of 228.2 ± 18.6 μm using an affordable 3D printer (<500 EUR). Notably, the HMA patch withstanded the forces exerted by thumb pressing (i.e. 20-40 N). Subsequently, the holes of the HMA enabled the fluid extraction tested in vitro and in vivo in plant leaves (i.e. 13.5 ± 1.1 μL). A paper-based sampling strategy adapted to the HMA allowed the collection of plant fluid. Finally, integrating the sampling device onto biosensors facilitated the in situ electrochemical analysis of plant health biomarkers (i.e. H 2 O 2 , glucose, and pH) and the electrochemical profiling of plants in five plant species. Overall, this electrochemical platform advances precise and versatile sensors for plant health monitoring. The wearable device can potentially improve precision farming practices, addressing the critical need for sustainable and resilient agriculture in changing environmental conditions. [Display omitted] • An affordable high resolution 3D-printed hollow microneedle array (<30 μm tip) is developed. • Full characterization of the fluid uptake including in vitro and in vivo tests (plant leaves) is provided. • A paper-based sampling strategy is used to interface the microneedle array and the sensor. • The electrochemical detection of plant biomarkers has been demonstrated on plant leaves. • The cost-effectiveness and scalability of the platform contribute to a faster transfer from lab to fab. [ABSTRACT FROM AUTHOR]

Hydrogen is an excellent energy carrier and considered a promising candidate to replace petroleum-based fossil fuels. But there are unsafe factors in the use process of hydrogen. Therefore, it is necessary to develop a commercially viable and highly reliable hydrogen sensor. Here, this review, the findings presented in recent research papers and future directions of solid electrolyte electrochemical hydrogen sensor based is introduced. We discovered that solid-state electrochemical hydrogen sensors have the advantages of portability, miniaturization, real-time monitoring, reliable and fast response. Future development directions will include improvement of material properties, high sensor responsiveness and durability, enhancement of integration and miniaturization, and new material systems, including nanomaterials, composite material. In the future, networking, intelligent and the trend of combining multiple technologies into smart/intelligent detection devices will favor the development of hydrogen sensors in a wide measuring range and better response time. [Display omitted] • Three types of solid-state electrochemical H 2 sensors are introduced. • Different electrode and electrolyte materials are presented. • The development prospect of solid-state electrochemical H 2 sensor is proposed. [ABSTRACT FROM AUTHOR]

Guanosine is an essential biomarker that enacts an important role in neuroprotection against brain-related activities, influences the metabolism of fatty acids, and assists in the improvement of the gastrointestinal tract. A facile and selective electrochemical sensor has been developed for the sensing of guanosine based on a hierarchical porous covalent organic framework. Owing to the distinctive 2D porous architecture and ordered framework of TpBD-COF, the irreversible electrooxidation of guanosine occurred at 1.03 V (vs. SCE) in phosphate buffer solution at pH 6. The anodic peak currents under optimal conditions were linear with guanosine concentration within the range of 0.123–720 μM with a LOD of 40.63 nM under various optimal conditions. Moreover, the developed biosensor was used to determine guanosine in pharmaceutical tablets to confirm its potential application in the healthcare industry. [Display omitted] • Hierarchical porous covalent organic framework-based sensor for guanosine detection. • The heteroatom functionalized structure boosted the electrochemical sensing ability. • It exhibited a broad linear detection range from 0.123 to 720 μM and achieved a low detection limit of 40.63 nM. • The sensor demonstrated excellent repeatability and reproducibility, indicating its reliability for guanosine detection. [ABSTRACT FROM AUTHOR]

• The α -Fe 2 O 3 nanomaterials were prepared using a simple one-step hydrothermal method. • S1-250 sensor has a lower operating temperature (225 °C) and the highest response(88.47/100 ppm). • The long-term stability, selectivity and resistance to moisture of the S1-250 sensor were better than that of the S2-350 sensor. • The structure-activity relationship between material structure and gas-sensitive properties is studied to provide new ideas for the design of gas-sensitive materials. In different environments, high concentration of n-butanol will have certain harm to the human senses and nervous system, meanwhile the electrochemical sensor limits its widespread use due to its high power consumption, so it is very meaningful to develop a semiconductor n-butanol sensor with low energy consumption. In this paper, α-Fe 2 O 3 nanorods were prepared by one-step hydrothermal method and then assembled into a n-butanol sensor capable of detecting n-butanol, and the effects of two different calcination temperatures on the performance of the sensor were investigated. Due to its higher Fe3+ content, higher oxygen vacancy content and larger specific surface area, S1-250 provided more active sites for gas adsorption, which making the response of S1-250 to 100 ppm n-butanol at 215 °C reached to 88.4. Finally, the effect of the calcination temperature on the sensor and the response mechanism were discussed. This paper offers promising applications for low-energy n-butanol sensors assembled from a single material α −Fe 2 O 3. [ABSTRACT FROM AUTHOR]

Carbon paper-based electrochemical sensors offer the possibility of long-term in vivo monitoring of the biomarkers due to their chemical stability and porous structure. However, the serious self-staking and aggregation of the carbon materials seriously block the diffusion of target biomolecules and limit the sensitivity and selectivity of the device. Here we report a controllable interfacial coupling strategy in which a composite paper electrode made by electrostatic self-assembling reduced graphene oxide (rGO) on carbon fiber (CF) modified with cationic polyacrylamide to avoid the self-stacking in scalable wet papermaking and thus increased accessible electrochemically active surface area and accelerate the diffusion of biomarkers. The resulting composite paper shows improved stability, high selectivity, long-durability, and excellent sensitivity in the electrochemical detection of biomarkers such as ascorbic acid, dopamine, and uric acid. Our approach, which combines mature industrial paper technology with interface engineering and electrochemical reduction, offers a potential avenue for low-cost and scalable implantable electrodes for timely and long-term monitoring in the surgical and clinical applications. [Display omitted] • RGO was uniformly coupled on the CFs assisted by interfacial CPAM molecules. • Large-scale preparation of electrodes through traditional wet papermaking. • Enlarged electrochemically active surface area of composite paper electrodes. • Excellent selectivity and sensitivity in detection of biomarkers such as DA. [ABSTRACT FROM AUTHOR]

• Development of a dual-templated molecularly imprinted electrochemical sensor for the simultaneous analysis of brilliant blue FCF and tartrazine. • MIP film was generated by electro-polymerization of 3-aminophenyl boronic acid with brilliant blue and tartrazine as templates. • High surface area modification enables the formation of complementary binding sites for both analytes on the MIP sensor surface during fabrication. • Successful application of the developed sensor in real food samples. In this study, a dual-templated molecularly imprinted polymer-based electrochemical sensor was developed for the simultaneous analysis of two food additive dyes, brilliant blue FCF and tartrazine. Using a 3-aminophenyl boronic acid (3-APBA) monomer and the dual templates of brilliant blue FCF (BB) and tartrazine (TZ), the molecularly imprinted polymer (MIP) layer was electropolymerized on the carbon fibre paper (CFP) electrode. By using BB and TZ as template molecules along the electro-polymerization of 3-APBA, then removing both template molecules, the MIP film was generated on the surface of the CFP electrode. Due to the high surface area provided by modification, several complementary binding sites for template molecules are formed on the surface of the MIP sensor during this process of sensor fabrication. On the MIP/CFP electrode, the electrochemical behavior of BB and TZ was assessed. The monomer/template ratio, pH values, and influencing parameters like the electro-polymerization scanning cycles were all optimized. This sensor was applied to detect brilliant blue FCF and tartrazine in beverage and food samples using MIPAPBA/CFP electrode. [Display omitted] Graphical representation of the sensor fabrication process [ABSTRACT FROM AUTHOR]

Designing and exploiting integrated electrodes is the current inevitable trend to realize the sustainable development of electrochemical sensors. In this work, a series of integrated electrodes prepared by in situ growing the second metal ion-modulated FeM-MIL-88 (M = Mn, Co and Ni) on carbon paper (CP) (FeM-MIL-88/CP) were constructed as the electrochemical sensing platforms for the simultaneous detection of dopamine (DA) and acetaminophen (AC). Among them, FeMn-MIL-88/CP exhibited the best sensing behaviors and achieved the trace detection for DA and AC owing to synergistic catalysis between Fe3+, Mn2+ and CP. The electrochemical sensor based on FeMn-MIL-88/CP showed ultra-high sensitivities of 2.85 and 7.46 μA μM−1 cm−2 and extremely low detection limits of 0.082 and 0.015 μM for DA and AC, respectively. The FeMn-MIL-88/CP also exhibited outstanding anti-interference ability, repeatability and stability, and satisfactory results were also obtained in the detection of actual samples. The mechanism of Mn2+ modulation on the electrocatalytic activity of FeMn-MIL-88/CP towards DA and AC was revealed for the first time through the density functional theory (DFT) calculations. Good adsorption energy and rapid electron transfer worked synergistically to improve the sensing performances of DA and AC. This work not only provided a high-performance integrated electrode for the sensing field, but also demonstrated the influencing factors of electrochemical sensing at the molecular levels, laying a theoretical foundation for the sustainable development of subsequent electrochemical sensing. Synopsis : In-situ construction of integrated electrodes of FeM-MIL-88/CP (M = Mn, Co and Ni) were constructed as electrochemical sensing platforms for trace detection of dopamine and acetaminophen based on crystal engineering strategy of second metal modulation. [Display omitted] • The integrated electrodes of FeM-MIL-88/CP based on the crystal engineering strategy were prepared by in situ growth method. • FeMn-MIL-88/CP exhibited ultra-high sensitivities and trace detection limits for the simultaneous detection of DA and AC. • Theoretical calculations were introduced to explore the electrochemical sensing mechanism. • Adsorption energy and electron transfer were the key factors affecting electrochemical sensing performances. [ABSTRACT FROM AUTHOR]

Smart wound dressings aim to enable early diagnosis and treatment of wound infections to accelerate wound healing. This paper summarizes the latest research progress of smart wound dressings, including smart dressings for monitoring different parameters of wounds, smart dressings that can realize wound management, and advanced smart wound dressings that integrate monitoring and treatment into one, and systematically discusses and analyzes them. [Display omitted] • A comprehensive review of the latest developments in intelligent wound dressings. • Explored various wound dressing design concepts and developed applications. • Discussed the future prospects and challenges of intelligent wound dressings. Wound management has long been a significant concern within the healthcare industry. However, conventional passive wound dressings often fail to meet the requirements for effective wound management. As a result, there is a growing emergence of intelligent wound dressings that aim to address this issue. These smart wound dressings incorporate one or more electrochemical or optical sensors, enabling real-time monitoring of wound conditions. Furthermore, they also integrate various stimulation techniques, including photostimulation, electrostimulation, and pharmacological stimulation, in order to facilitate accelerated wound healing. This integration of sensing and stimulation capabilities holds immense potential for personalized wound care. This paper offers a comprehensive review of recent advancements in the field of wearable, novel dressings designed for the purpose of chronic wound monitoring and management. It examines various design concepts and applications that have been developed. Additionally, the paper discusses the future prospects and challenges associated with wearable bioelectronics in wound care, as well as their potential for clinical utilization. Furthermore, it explores the areas in which further development and research are needed, with a focus on establishing the priorities for the next generation of wound dressings. [ABSTRACT FROM AUTHOR]

• Indium sulfide (In 2 S 3) has emerged as a potential nanomaterial for sensing applications. • In 2 S 3 -based nanomaterials showed excellent gas and electrochemical sensing characteristics. • Recent developments in the gas and electrochemical In 2 S 3 -based sensors have been summarized. • Current challenges and futuristic ways to enhance sensing performance have been discussed. Due to their superior sensing characteristics, In 2 S 3 -based nanocomposites have emerged as attractive materials in gas and electrochemical sensors in recent years. This review article gives an in-depth look at the most recent advancements in using In 2 S 3 as a fundamental component in sensor applications. The discussion begins with an overview of In 2 S 3 as a sensor material, including its intrinsic features and gas and electrochemical detection possibilities. The study digs into In 2 S 3 ′s gas and electrochemical sensing methods, clarifying the processes that underpin its sensitivity to specific analytes. It investigates the interaction of In 2 S 3 with target gases or ions, emphasizing the significance of surface chemistry, charge transfer, and structural alterations in the sensing process. This review paper focuses on recent gas and electrochemical sensing advances made by In 2 S 3 -based nanocomposites. Researchers improved sensor performance by integrating In 2 S 3 into diverse composite architectures. It also includes case studies and effective examples of In 2 S 3 -based nanocomposites in real-world sensing applications. These examples illustrate the sensors' usefulness and adaptability in detecting a wide range of gases and ions with great sensitivity and selectivity. In summary, this review paper provides an in-depth look at the most recent advancements in In 2 S 3 -based nanocomposites for gas and electrochemical sensors. It provides an excellent resource for academics, engineers, and professionals by illuminating sensing mechanisms, stressing essential parameters, highlighting current discoveries, supporting further innovation, and the broader application of In 2 S 3 -based nanocomposite sensors. [ABSTRACT FROM AUTHOR]

Advancements in wearable technologies in the past few years have influenced the fabrication of fiber-based supercapacitors and sensors for next-generation energy-autonomous systems. There has been an increase in research on conductive electrodes on fibers for sensing ability and storing of energy based on their ease of fabrication, stretch and flexible abilities. These replace the conventional rigid devices that limit the flow of air and provide discomfort when used in clothing. Fiber-based sensors are generally fabricated to detect environmental and physiological changes in real-time. They are mostly fabricated for use as temperature, photo, chemical, and tactile sensors using different applications, and materials. A variety of wearable physical, chemical, biological, and optical sensors that have been described as self-powered or energy-autonomous in recent years rely on these technologies, as well as energy generators, electrochemical energy storage (EES) systems, wireless power technologies, self-powered sensors, and hybrid energy systems that combine energy generators and electrochemical energy storage. This paper highlights a comprehensive review of the recent advancements in fiber-based and sensors for supercapacitors energy-autonomous systems. The paper further highlights fiber-based material properties, such as lightweight, flexibility, high surface area, and their impact on energy density and stability. The paper also discusses the various fabrication methods for fiber-based supercapacitors and sensors, including electrospinning, dip-coating, and self-assembly. Finally, the paper elucidates future directions of fiber-based sensors and supercapacitors for electrochemical energy storage and visa vis sustainable production. Fibers and their related composites have been considered for the fabrication of SCs and sensors, which find applications in energy-autonomous systems. Herein, we describe the fabrication methods and present recent advances in natural-based and synthetic-based composites used for SCs and sensors. Lastly, we highlight future research directions toward a more sustainable material and production. [Display omitted] • An overview of fiber-based sensors and supercapacitors (SCs) for energy-autonomous systems (EAS) is presented. • Fiber-based sensors and supercapacitors are made from natural, synthetic and carbon-based composites. • Fiber-based supercapacitors have long life cycle and high energy density for wide EAS applications. • Lightweight/flexible fiber-based sensors enhance applications in medical diagnostics and environmental sensing. • Sustainable fiber-based sensors and SCs in line with UN-SDG are being researched. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrogen peroxide (H 2 O 2) is produced through the single electron reduction of oxygen in organisms, playing a crucial role in cell signaling and maintaining internal stability. Exploring a simple yet effective method for real-time and quantitative detection of H 2 O 2 in living cells and actual samples holds immense significance. The use of nanocatalysts as sensing materials in the electrochemical detection method has garnered significant attention due to its operational simplicity, high sensitivity, cost-effectiveness, and easy miniaturization. This paper focuses on summarizing contemporary techniques for H 2 O 2 detection, particularly emphasizing electrochemical methods, and highlights significant advancements in electrochemical detection of H 2 O 2 nanomaterials, providing insights into future developments. • Introducing the current methodologies for H 2 O 2 detecting. • Providing a comprehensive overview of non-enzyme nanocatalysts designed for electrochemical H 2 O 2 detection. • Exploring the prospects in the realm of electrochemical detection using non-enzyme catalysts. With the progression of society, an increasing emphasis on physical well-being and environmental safety has driven extensive research into technologies closely aligned with human health and environmental protection. Hydrogen peroxide (H 2 O 2), a representative reactive oxygen species (ROS), serves as one of the products resulting from the single electron reduction of oxygen in organisms, playing a crucial role in cell signaling and maintaining internal stability. Relevant alterations of H 2 O 2 concentrations have been implicated in the pathogenesis of various diseases, including diabetes and cancer. Moreover, the utilization of H 2 O 2 is widely prevalent in various industries including chemical, pharmaceutical, and food sectors. However, the repetitive or uncontrolled utilization of H 2 O 2 engenders deleterious implications for human well-being and environmental integrity. Therefore, there is immense significance in exploring a simple yet effective method for real-time and quantitative detection of H 2 O 2 in living cells and actual samples. The use of nanocatalysts as sensing materials in the electrochemical detection method has garnered significant attention from researchers due to their operational simplicity, high sensitivity, cost-effectiveness, and facile miniaturization. However, there remains a dearth of comprehensive reviews on the electrochemical detection of H 2 O 2 utilizing nanomaterials. In this paper, we focus on summarizing contemporary techniques for H 2 O 2 detection with a specific emphasis on electrochemical detection methods, and highlighting the significant advancements in the field of electrochemical detection of H 2 O 2 nanomaterials while also providing insights into future developments. [ABSTRACT FROM AUTHOR]

• Fluorescence and electrochemical sensors for sensitive Tartrazine (Tar) detection in foods are explored. • Advanced carbon-based nanomaterials enhance Tar detection in food, boosting safety. • Electrochemical sensors rapidly spot Tar in food with high sensitivity. • This work focuses on refining sensitivity and selectivity, addressing challenges in Tar detection for safer food. • The review highlighted future research, multifunctional sensors & portable device integration. Azo dyes are widely used as food coloring agents because of their affordability and stability. Examples include brilliant blue, carmoisine, sunset yellow, allura red, and tartrazine (Tar), etc. Notably, Tar is often utilized in hazardous food goods. They are frequently flavoured and combined with food items, raising the likelihood and danger of exposure. Therefore, detecting Tar in food is crucial to prevent health risks. Fluorescence nanomaterials and electrochemical sensors, known for their high sensitivity, affordability, simplicity, and speed, have been widely adopted by researchers for Tar detection. This comprehensive paper delves into the detection of Tar in food products. It extensively covers the utilization of advanced carbon-based nanomaterials, including CDs, doped CDs, and functionalized CDs, for sensitive Tar detection. Additionally, the paper explores the application of electrochemical sensors. The paper concludes by addressing current challenges and prospects, emphasizing efforts to enhance sensitivity, and selectivity for improved food safety. [ABSTRACT FROM AUTHOR]

[Display omitted] • A scalable and automated method to fabricate electrochemical sensors. • CO 2 laser source generates carbon conductive tracks onto Kapton tapes. • Sensors can be made with different geometries and sizes. • Disposable, versatile, and miniaturized devices for field analyses. • Portable microfluidic platforms are created by integrating paper with the sensors. The laser scribing technique produced disposable electrochemical devices with Kapton adhesive tape as a polyimide substrate. The approach consisted of carbonizing the polyimide substrate with a CO 2 laser source, generating the 3-electrode electrochemical system based on carbon conductive tracks. The materials were characterized by Raman spectroscopy, scanning electron microscopy, and electrochemical techniques. The laser processing parameters were submitted to the optimization process, demonstrating a strong impact on the electrochemical properties of the sensors. The sensors were initially fabricated in a chip format, providing satisfactory electrochemical responses compared to commercial screen-printed electrodes. In addition, they showed reproductivity, repeatability, and storage stability. Once characterized, the sensors were combined with paper devices to show the versatility of the electrochemical system. Paper was chosen because of its ubiquity and ability to generate flow without external pumps, resulting in portable analytical platforms. This combination can be advantageous for point-of-need applications. The analytical performance of the devices was evaluated for voltammetric determination of 3-nitrotyrosine, uric acid, and dopamine, demonstrating attractive features for analytical applications. [ABSTRACT FROM AUTHOR]